The pattern of feckless inattention that, in 2005, resulted in more than 400 development violations in Clarksburg is about to be repeated. This time it imperils one of the last unspoiled creeks in Montgomery County — Ten Mile Creek — with serious consequences for the whole region.

Ten Mile Creek runs steady, clean and cold. It harbors a greater abundance and diversity of life — from salamanders to stoneflies — than other streams in the region. It empties into Little Seneca Lake, the emergency water supply reservoir for metropolitan Washington via the Washington Suburban Sanitary Commission’s intake on the Potomac River.

But its high water quality is threatened by two major development projects that have gathered momentum in the absence of action by the Montgomery County Council to protect the creek, now pending for more than two years.

When the council approved the Clarksburg master plan in 1994, it waffled on protection of Ten Mile Creek. Proclaiming the stream critical, it placed the western side of the watershed in the county’s Agricultural Reserve, safeguarding the farms and forests that had occupied it for generations. The eastern side was designated for possible development, but recognizing that splitting a sensitive watershed up the middle would be hydrologically challenging, the council postponed decisions on extending a sewer service up the stream valley and rezoning for higher densities until studies determined whether the best stormwater management practices required for development in the Little Seneca watershed could adequately protect the stream. Those studies, completed in 2009, concluded they could not.

The Montgomery County Planning Board (I was chairman at the time) and the County Department of Environmental Protection recommended that a master plan amendment be prepared to designate more appropriate land uses and resource protection measures for the eastern watershed. Instead, the council appointed an Ad Hoc Water Quality Working Group to propose a course of action. That group reported in 2010. The majority recommended a master plan amendment to reduce densities on land between the stream and Interstate 270 and require a science-based cap on impervious surfaces for the entire watershed, which includes land in the headwaters east of I-270.

In the meantime, however, two development proposals for land in the headwaters are being dangled before the Clarksburg community. They would bring more than a thousand housing units and a half-million square feet of commercial space into the headwaters of Ten Mile Creek. The scale and footprint of these projects, along with the sewer lines to serve them, will destroy this sensitive watershed. Proponents of development in the Ten Mile Creek watershed apparently hope that local eagerness for a commercial district will overcome any sense of responsibility for protecting the stream and that decay of official memory will allow town center developers off the hook on which they have placed themselves. This insult to the environment should not be added to Clarksburg’s manifold injuries.

The council should authorize the Planning Board to prepare a master plan amendment that recognizes the findings of the watershed studies, proposes policies that can protect the Ten Mile Creek watershed and establishes science-based caps on impervious surfaces in the watershed — especially in its headwaters. The board should also take measures to achieve development of the approved Clarksburg Town Center’s community and market center. Combining rural land and stream protection with effective density levels and amenities in its town center would make Clarksburg the smart-growth model the master plan intended it to be. The council needs to act now. Key votes are due in October, and the clock is ticking.

The writer was chairman of the Montgomery County Planning Board from 1972 to 1981 and 2006 to 2010.